Abstract: The invention can be summarized as follows. There is provided a method of bleaching chemical pulp comprising the steps of exposing chemical pulp to a chemical bleaching state to produce a partially bleached pulp and treating the partially bleached pulp with a thermophilic, alkalophilic xylanase in an alkaline extraction stage at pH of 8 to 14. The method may be performed in a mill and may form part of a more complex pulp bleaching process. The invention also relates to the use of a thermophilic, alkalophilic xylanase in an alkaline extraction stage of a pulp bleaching process in a mill.

Abstract: The present invention discloses methods of bleaching chemical pulp that use xylanase enzymes after chemical bleaching. The method comprises the steps of carrying out a chlorine dioxide stage to produce a partially bleached pulp, treating the partially bleached pulp with a xylanase enzyme, optionally in the presence of oxygen and hydrogen peroxide, in a mild extraction stage, then bleaching the pulp with a second chlorine dioxide stage. The method allows the mill to decrease the usage of sodium hydroxide or other alkali, while decreasing the use of chlorine dioxide, and possibly improving the yield and strength of the pulp, while maintaining a similar level of bleached brightness of the pulp. The pulp bleaching method of the present invention may be performed in a pulp mill as part of a complex pulp bleaching process.

Abstract: A method of bleaching chemical pulp with xylanase after chemical bleaching is provided. The method comprises the steps of exposing chemical pulp to a chlorine dioxide bleaching stage to produce a partially bleached pulp, treating the partially bleached pulp with a xylanase in an enzyme treatment stage at a pH of about 3 to about 8, then carrying out an alkaline extraction of the pulp. The pulp bleaching method of the present invention may be performed in a pulp mill as part of a complex pulp bleaching process.

Abstract: The present invention discloses methods of bleaching chemical pulp that use xylanase enzymes after chemical bleaching. The method comprises the steps of carrying out a chlorine dioxide stage to produce a partially bleached pulp, treating the partially bleached pulp with a xylanase enzyme, optionally in the presence of oxygen and hydrogen peroxide, in a mild extraction stage, then bleaching the pulp with a second chlorine dioxide stage. The method allows the mill to decrease the usage of sodium hydroxide or other alkali, while decreasing the use of chlorine dioxide, and possibly improving the yield and strength of the pulp, while maintaining a similar level of bleached brightness of the pulp. The pulp bleaching method of the present invention may be performed in a pulp mill as part of a complex pulp bleaching process.

Abstract: The present invention discloses methods of bleaching chemical pulp with xylanase after chemical bleaching. The method comprises the steps of treating chemical pulp with a first xylanase in a first enzyme treatment stage to produce an enzyme treated pulp, exposing the enzyme treated pulp to a chemical bleaching stage to produce a partially bleached pulp, and treating the partially bleached pulp with a second xylanase in a second enzyme treatment stage at a pH of about 3 to about 8. Further, there is disclosed a method of bleaching pulp comprising the steps of exposing chemical pulp to a chlorine dioxide bleaching stage to produce a partially bleached pulp, treating the partially bleached pulp with a xylanase in an enzyme treatment stage at a pH of about 3 to about 8, then carrying out an alkaline extraction of the pulp. The pulp bleaching method of the present invention may be performed in a pulp mill as part of a complex pulp bleaching process.